Inhibiting corrosion in wells



Patented Nov. 16, 1948 aisassa INHIBITINGI'COBROSION 1N WELLS PrentissS. Viles and Elza Q. Camp, Goose Creek, Tex., assignors to StandardOilDevelopment Company, a corporation of Delaware No Drawing.

Application January 24, 1946, Serial No. 643,207. 1

6 claims. ((31. 252-4555 The present inventionis directed to theproduction of fluids from underground formations. More particularly, theinvention is directed to protecting the conduits and attendantequipment, through which fluids from subsurface formations are flowedand processed, from corrosion by materials occurring in or areintroduced into fluids originating in subsurface format1ons.

In many oil, gas, and condensate fields, the production of fluid fromsubsurface formations is accompanied by extremely severe corrosion ofthe conduits and attendant equipment which comes into contact with thefluid mixture being produced. In many cases it is found that the fluidmixture is acidic in nature and comprises substantial amounts of carbondioxide, a portion of which dissolves in water present to form carbonicacid. In addition to the carbon dioxide other materials which arepresent in the corrosive mixture may include organic acids. inorganicacids, inorganic salts and acidic sulfur compounds. These corrosivesubstances occur in or are introduced into the fluids originating in thesubsurface formations. In some cases the corro sion occurs throughoutthe conduits and attendant equipment through which the fluids from thesubsurface formations are flowed and processed.

In other cases the corrosionis limited primarily to portions of theconduits near the surface of the wells and to the well-head andattendant equipment. In all cases it has been necessary to makeextensive replacements of equipment that has failed as a result ofcorrosion. This not only limits production, but is extremely expensive,particularly in those cases in which it is necessary to kill a highpressure well in order to make repairs and to replace corrodedequipment. In addition to the high costs of making repairs to wellequipment, there is a marked loss in revenues due to having a well offproduction and to the necessity of having ,to maintain additional wellsand sources of supply to meet production requirements during periods inwhich a Well is off production for repairs as a result of corrosion.Further, there is constant danger that a Well will flow wild as a resultof the failure of equipment due to corrosion. In cases of this kind,enormous losses are incurred.

It is, therefore, the main object of the present invention to provide amethod whereby corrosion is substantially eliminated or inhibited in theconduits and attendant equipment through which fluids from subsurfaceformations are flowed and processed,

In accordance with the present invention,

acidic corrosion of metallic surfaces is inhibited or substantiallyeliminated by adding small amounts of sulfur to fluids produced from subsurface formations which are acidic in nature and include carbondioxide. l

The amount of sulfur employed toinhibit the corrosion of the ferrousmetal surfaces by the fluid mixtures produced from subsurface formationsmay be varied over a wide range and satisfactory results obtained.Inasmuch as sulfur is usually an undesirable constituent in. thehydrocarbon fluid being obtained, it is preferable to employ only smallamounts of the sulfur to inhibit the corrosion but in some cases the useof large amounts of sulfur may be desirable or necessary and in suchinstances the sulfur may be added in amounts up to 3% by weight based onthe weight of fluid mixture produced from the subsurface formation.I-Iowever, it will usually be found that minor amounts of sulfur will beeffective for inhibiting corrosion of the ferrous metal surfaces and,accordingly, under many operating conditions the sulfur used foreffectively inhibiting corrosion may be .1% or even as low as .01'%

by weight of the fluid mixture being produced.

It may be found that after an effective amount of sulfur has beenemployed to inhibit corrosion.

of the ferrous metal surfaces, a lower amount maintained in the fluidmixture will be effective thereafter to maintain the inhibiting effect.Accordingly, a substantial amount of sulfur as of the order of 1% byweight of the fluid produced, may be employed for a period sufficient tocause corrosion of the ferrous metal surfaces to be effectivelyinhibited and thereafter much smaller amounts, as of the order of .01%of sulfur based on the weight of the fluid produced, may be employed tomaintain the inhibited condition of the metallic surfaces.

It will be found convenient to suspend or dissolve the sulfur in asuitable vehicle before introducing it into the fluid mixture. Theresultant suspension or solution may then be conveniently injected intothe borehole adjacent the subsurface formation from which the fluid isproduced or may be introduced into the conduit through which the fluidmixture flows from the subsurface formation to the surface of the earth.Another method of employing the inhibiting agent is by injecting thesuspension or solution into the subsurface reservoir by employing anadjacent well; it will be apparent that when adding the inhibiting agentin accordance with this Drocedure, the fluid entering the borehole ofthe producing well will comprise th'e inhibiting agent.

Test pieces of carbon steelwere immersed in water solutions under apressure of 100"lb's, per

sq. in. gauge of carbon dioxide and thez-test pieces were maintainedunder this pressure for anzi'n terval of 24 hrs. and at a temperatureof1'70! F. The carbon dioxide was admitted to the system through apressure regulator valve thus maintaining a constantpressure of carbondi'ox I id'e'-onthe system so that the water solutions in whichthea'carbon steel test specimens wereimmersed':.we're" saturated withcarbon dioxide at the temperatures and pressures at' wh'ich -thetestswere conducted? One of the solutionswas employediash-sa. blanlvwith i-noinhibiting material added-"while another. 1 solution has: added theretoanainhibitingmaterial comprising elemental sulfur dissolved inhydrocarbons in an amount of 1 'sulfur:and!20:%hydrocarbons by-weight inthe solutiom. The results obtained? by --the"t'e'sts'- areshown'mmherfol'lowing' table:

Table.

1 h Reduction of Corrosion InhibitingMater'ial. Rate, Inches gggigfig IperYear Per Cent None 0. 2250 Free-sulfur'dissolvcd iii-Hydrocarbons0.0405 82.1

It? will be. observed from. the data-presented in. the foregoing. table;that, the addition of; a smal1.-

amount of ,elemental sulfur effects-a markedrreduction in the,.tendencyofacorrosive water-solu tion to corrodecarbon steel.

The; nature and objects of the present invention having been fullydescribed and illustrated, what We desire to claim as new and useful andto secure by Letters Patent is:

1. A method for. reducing the corrosiveness to corrodible ferrous metalof a corrosive fluid including moisture and carbon dioxide whichcomprises introducing into said fluid a corrosion inhibiting'amount ofelemental sulfur.

2. A method in accordance with claim 1 in which the elemental sulfuradded to the corrosive fluid is. in an. amount up to 3% by weight of thefluid.

3;:A methodaccordance with claim 1 in which the elemental sulfurintroduced into said fluid is in the range of 0.01% to 1% by weight of4;:-A=:method for reducing the corrosiveness to corrodible ferrous metalof a corrosive fluid including a major portion of hydrocarbons and aminor portion of moisture and carbon dioxide whichicomprisesintroducinginto said fiuidacorrosion inhibiting-amount of elemental'sulfur.

5. A method in accordance with claim 4 in which, said ferrous metal is aconduit through which said corrosive fluid is withdrawn from asubsurface formationand in which said elemental sulfuris introduceddirectly into said conduit.

6.- A method in accordance with claim 4 in;

which theelemental sulfur introducedinto said fluid is in the rangeof"0.0 to 1% by weight of the fluid.

PRENTISS S. VILES. ELZA'Q. CAMP;

REFERENCES CITED 'I.l"'1e-following references are of'record'in the fileofz'this patent:

UNITED STATES PATENTS Number Name Date 1,829,705" Walker I Oct. 27, 19311,873,084 Walker II .Aug. 23, 1932 2,147,155 Gardner Feb. 14, 19392,222,431 Colin Nov. 19, 1940 2,258,806 Pier etral; Oct. 14, 1941? OTHERREFERENCES Industrial and-Engineering Chemistry, vol. 38, pp.. 10. and14, Jan. 16,- 1946.

